Demonstrators launch firecrackers outside the U.S. Embassy during a protest in La Paz, Bolivia, on July 8. / Juan Karita, AP

by Michael Winter, USA TODAY

by Michael Winter, USA TODAY

An apparent al-Qaeda threat to U.S. diplomatic facilities in Muslim countries prompted the State Department on Thursday to order that all American embassies and consulates be closed Sunday, several news organizations are reporting.

State Department spokeswoman Marie Harf said only during a daily news briefing in the morning that "certain" U.S. sites normally open on Sundays would close "out of an abundance of caution and care for our employees and others who may be visiting our installations."

She cited unspecified "information" about a threat to overseas facilities but did not say which or how many diplomatic outposts would be closed for the day, the beginning of the workweek in the Middle East, South Asia and North Africa. U.S. embassies and consulates elsewhere are normally closed on Sundays.

She said some facilities could be closed additional days "depending on our analysis."

NBC News, citing unidentified U.S. officials, reported later that the threat "appeared to have originated somewhere in the Middle East and to be related to al-Qaeda."

CBS News, also citing unnamed officials, reported that intelligence did not indicate a specific location or locations, and that the threat "appears to be a real plot in the making and not just the normal chatter among terrorists talking about attacks they'd like to carry out."

Another unidentified U.S. official told CNN that the Obama administration was taking the threat "very seriously."

The last major warning came in September, when U.S. diplomatic facilities across the Muslim world were warned of potential violence around the anniversary of the 9/11 attacks.